Since the dawn of the automotive age, literally thousands of sound attenuation devices, i.e., mufflers, have been designed in controlling the noise that is characteristic of the exhaust of an unregulated internal combustion engine. However, despite the considerable effort that has heretofore been put forward in providing effective sound attenuation for internal combustion engines, still further improvement in the art is needed. This is particularly true in the case of high performance engines intended for use in automobile racing, boat racing, aircraft racing, off-road applications, industrial applications, and the like. This is true because high performance engines often have cam shafts and compression ratios which differ markedly from those of conventional automobile engines, and are often provided with exotic fuels which have operational characteristics which differ markedly from those of conventional gasoline.
The problem in designing a workable sound attenuation device for high performance engines stems from the fact that sound attenuation devices used in conjunction with internal combustion engines perform two functions in connection therewith. As will be apparent, the first function is that of controlling the exhaust noise generated by operation of the engine. The second function involves controlling the back pressure of the exhaust of the engine. Exhaust back pressure control is essential because when the back pressure is too low the engine tends to overheat, leading to burned valves, etc. Conversely, when the back pressure is too high, the performance of the engine is diminished, a condition which cannot be tolerated in high performance engines. Consistency in exhaust back pressure is also important in order that the engine will run reliably.
For example, in high performance race-car engines, it is common to use a different size exhaust tube, or meter tube, connected to each cylinder of the engine in an attempt to maintain the same exhaust back pressure on each cylinder. The present invention allows all of the cylinders to be manifolded into a common passageway which discharges through the present invention and the sound attenuation device of the present invention holds a constant back pressure on all engine cylinders.
The present invention is a sound attenuation device for internal combustion engines which fulfills the foregoing and other requirements long since found lacking in the prior art. In accordance with the broader aspects of the invention, a sound attenuation device comprises a tubular core having a hollow interior extending from an inlet to an outlet. The tubular core has a plurality of relatively small openings formed therein at axially and circumferentially spaced apart locations. One or more flanges extend radially outward from the tubular core and position in the tubular core in the center of an exhaust passageway. Each flange has a plurality of relatively large perforations extending therethrough.
In the operation of the sound attenuation device a portion of the exhaust gases flowing through the exhaust passageway flow through the hollow interior of the tubular core. The remainder of the exhaust gases flow around the exterior of the tubular core through the perforations in the flange(s). The openings in the tubular core allow fluid communication between the interior and exterior thereof. The exhaust gases are recombined at the outlet of the tubular core.
In accordance with a first embodiment of the invention, the hollow interior of the tubular core is unrestricted throughout its length. In accordance with a second embodiment of the invention, the tubular core is provided with end-caps, including an inlet end-cap which is closed and an outlet end-cap which has a relatively small diameter passageway formed therethrough. This construction reduces the percentage of exhaust gases flowing into the interior of the tubular core.
It is an advantage of the present invention to provide a sound attenuation device which equalizes the exhaust back pressure on all cylinders of an internal combustion engine, thereby improving efficiency and increasing performance.
It is an advantage of the present invention to provide a sound attenuation device for internal combustion engines which eliminates the need for an enlargement in diameter in the exhaust passageway, which may be inserted in the existing exhaust pipe of the engine or which may be encased in a housing and connected to the discharge end of the exhaust pipe, and which is approximately ten percent (10%) of the weight of a conventional muffler.